Explosive jarring device



Dec- 6, 1955 o. J. MGcULLoUGH EXPLOSIVE JARRING DEVICE JNVENTOR. 0. J.MCCLLfmg/z Ham Filed NOV. 8. 1950 ATTORNEY nited States Patent-"O A2,725,820 EXPLOSIVE JARRIN G DEVICE @tis Johnson McCulloughHouston,Tex., assignor to McCullough Tool Company, Los Angeles, Calif., acorporation of Nevada Application November 8, 1950, Serial No. 194,600 3Claims. (Cl. 102-20) This invention relates to a jarring device forloosening or releasing pipe which has become stuck in a well, andparticularly to an explosive type jarring device for this purpose. p

In conventional rotary drilling, a tubular drill stem carrying a bit atitslower end is rotated to cut the well bore and lluid is circulatedthrough the bore of the drill stem and bit passages into and through theannular space between the wall of the well bore and the drilling stringto wash out the drill cuttings, plaster the Wall of the well bore, etc.During the course` of such drilling, the dn'lling string is continuouslysubject to becoming stuck in the well bore, due to caving of the walls,settling of drill cuttings about the bit and various other causes. Themost common danger results from settling of the cuttings about the bitshank, particularly when the circulation of drilling fluid and rotationof the string must be interrupted to add pipe sections to the drillingstring or to Withdraw the string from the well bore. As the bit isnormally larger in diameter than the balance of the drilling string, ashoulder or enlargement will necessarily be present adjacent the pointof connection of the bit shank to'the drill stem, and this shoulderprovides lodgment for cuttings, wall cavings and other detritus, which,if allowed to accumulate sufliciently will cause the drill bit to becomeanchored or stuck in the well bore so that it cannot be withdrawn. t Y

Such accumulation of detritus about the upper end of the drill bit is aprogressive phenomenon and the accumulation usually will rapidly becomeincreasingly large and more consolidated if prompt action is not takento remove the accumulation or free the bit from its sticking action,with the result that the bit willrbecome' increasingly l'irmly stuck sothat it cannot be withdrawn from the well. This will necessitate-breaking or cutting the drill pipe as close as possible to the pointwhere the sticking occurs, followed by a ditlicult and expensive fishingjob to remove the bit and clear the well bore for further drilling. j

Since sticking of the drill strings most often occurs immediatelyadjacent the bit, generally as a result of relatively smallaccumulations of detritus about the bit shank, it is found that it willvery often be possible to free the bit by applying a sharp jarring orshaking action to the portion of the string adjacent the bit and thearea of the accumulation, particularly if such jarring action is appliedpromptly after sticking rst occurs and before the accumulation becomesvery large or strongly consolidated.

Heretofore, various jarring tools have been employed in rotary strings,which generally comprise a relatively complicated tool composed ofrelatively movable parts which is installed as a part of the rotarystring, and is operated usually by appropriate manipulation of thedrilling string to produce the desired jarring action, which isprimarily an axial impact. Such conventional jarring tools arerelatively expensive to construct and as they introduce moving partsinto the drilling string, may become broken or jammed, with resultingineffectiveness in performing their designed function. Also the designof such tools almost always introduces a restriction in the bore of thedrilling string which cuts down the free circulation of drilling fluidthrough the string.

The present invention has for its primary object the provision of arelatively simple jarring device which obviates the principaldisadvantages of existing jarring tools.

A principal object is to provide an explosive type jarring device whichmay be introduced into the bore of the drilling string when and asrequired, particularly as soon as sticking occurs, to apply a jarring orshaking action in the drill string adjacent the point at which it hasbecome stuck.

Another object is the provision of a jarring device insertable in thebore of the drilling string and employing a exible string-type explosivebody adapted to extend longitudinally through the bore of the portion ofthe drilling string to which the jarring force resulting from detonationof the explosive body is to be applied.

A more specific object is the provision of a jarring device insertablein the bore of a drilling string and employing a flexible string-typeexplosive body, attached at its lower end to a weighted head carrying apercussion type detonator and connected at its upper end to a oatadapted to buoyantly support the explosive body in extended position inthe llnids normally present in the bore of the drilling string.

Other and more specific objects and advantages of this invention willbecome apparent from the following detailed description when read inconjunction with the accompanying drawings which illustrate usefulembodiments in accordance with this invention.

In the drawings:

Fig. l is a longitudinal, partly sectional, view of a well bore and adrilling string showing the manner in which the jarring device inaccordance with this invention may be employed for jarring the string;

Fig. 2 is a longitudinal, partly sectional, view of the jarring devicein accordance with one embodiment of this invention;

Fig. 3 is a fragmentary view illustrating a modilication of initiatingelements employed for setting off the explosive elernent; and

Fig. 4 shows a detail of a modified arrangement of the explosive elementemployed in the jarring device.

Fig. 2 of the drawings illustrates the details of a jarring device inaccordance with one embodiment of this invention. The device includes ahead member, designated generally by the numeral 10, which is connectedto the lower end of strand of exible cord-type explosive element 11, theupper end of which is connected to a buoyant lloat element 12. The partsof the device are shaped and dimensioned to be readily insertible in thebore of a drilling string.

Head member it) is a generally cylindrical body constructed of steel,lead or other heavy metal sufficiently heavy to cause the device to sinkrapidly through the drilling iiuid normally circulated through the boreof a drilling string. Head 10 is composed of upper and lower sections 14and 15, respectively. Upper portion 14 is provided with an upwardlyextending portion 16 of reduced diameter, and an externally threadedhollow tubular boss 1'7 extending from the lower end thereof andconcentric with the longitudinal axis of the head. Lower portion 15 hasan internally threaded socket 18 into which boss 17 is screwed toconnect the two sections of the head together and form a closed hollowchamber 19 within the body. A packing ring 2G is arranged between theinter-engaged threaded portions of boss 17 and socket 18 to seal thethreaded connection against leakage of fluid from outside the head intochamber 19. A narrowaxial passageway 21 extends through upper section 14and communicates with chamber 19. The lower end of passageway 21 isenlarged in diameter to receive a threaded tubular bushing 22, havingajbore 23 which is adapted to receive a percussion-type explosiveblasting cap 24, of generallyconventional form, which is inserted intobore 23 from the lower end thereof, to fire upwardly toward passageway2l. Lower end wall 25 of lower head section 15 is provided with an axialpassagewayvild, in which is slidably mounted a tiring pin 27 registeringwith cap 24. Firing pin 27 is normally maintained in retracted positionrelative to cap 24 bymeans of a shear pin 28 which extends transverselythrough the b ody of tiring pin 27 exterlorly ofend wall 25. A suitablelock ring or lug 2 9 is carried by the inner 'end of firing pin 27 toprevent its complete retraction from head section 15. The outer endfring pin 27 is provided with an enlarged head 30 and a packing ring 31is circumferentially arranged between firing pin 27 and the wall ofpassageway 26 to form aA fluid-tight' seal between the tiring pin andpassageway 26.

Explosive element 11, may be any suitable flexible cord-type explosivesuch as the well known Primacord, such as that manufactured by theEnsign-Biekford Cornpany, Simsbu'ry, Conn., which, generally speaking,is composed of a hollow fabric or plastic tube, the bore or which islled with one of the well known detonatable chemical explosives such aspentaerythritoltetranitrate, which may be tired by applying a detonatingshock at one end, the detonating wave travelling sufficiently rapidlythrough the length of the cord to produce substantially simultaneousdetonation throughout the whole length of the explosive comprising thecord.

One end of element 11 is inserted into passageway 2l in' juxtapositionto the discharge end of cap 24. A pellet 32 of any suitable boosterexplosive may be inserted in passageway 21 between vthe ends of element11 and cap 24 to intensify the detonating shock transmitted from theexplosion of cap 2410 the end of the explosive cord. An adhesive plasticseal 33, or any suitable type, is arranged about the point' of entry ofelement 11 into extension 26 to form a uid-tight seal about the outerend of passageway 24% and to fasten element 11 to head 1li. The oppositeend of element 11 is connected in any suitable manner to a bail 34carried by the lower end of oat 12. The end of element l1 may beconnected to the float by looping it through bail 34 and tying the endto the main portion of element 11 in the manner illustrated. The exposedend of element 11 is sealed by enclosing it in a mass of a suitablewater-repellant plastic material 35 in the manner shown.

Float 12 may be a closed hollow metal casing, as illusy trated, or maybe constructed of any other' suitable buoyant material., such as wood,plastic or the like. It should be designed to possess a degree ofbuoyancy sufficient only to support the weight of explosive element 11without oifering serious resistance to the sinking of the device as I :iwhole in the iluid which may be present in the bore of the pipe stringin which it is to be inserted. FEhe purpose of loat 12 is to maintainelement 11 in fully extended position while the device is passingdownwardly through the fluid in the drill pipe and, particularly, whenit attains the position therein at which the explosion of element 11 isto be effected.

Fig. l illustrates the manner in which the above described device may beemployed. There is shown a Well bore 36 being drilled by a conventionalrotary bit f 37 driven by a hollow drill pipe 38 which extends to thesurface and through which drilling uid 39 is circulated down through thebore of the drill pipe and through passages 40 provided in bit shank 41of the bit. Bit shank 41 provides the usual means for connecting the bitto drill pipe 38 and also forms an internal stop in theV bore of thedrill pipe at a point closely adjacent the bit. When sticking of the bitoccurs, as by accumulation oi detritus 43 on' the upper outer' surfacesof the bit and the adjacent portion of the drill pipe, the drille'r willinsert the jarring device, above described, into the bore of `the drillpipe at the surface. The weight of head 10 will cause the device to sinkrapidly through fluid 39, explosive element 11 being held in extendedposition by the resistance oiered by the buoyancy of float 12 in fluid39. When the downwardly extending end of ring pin 27 strikes the end ofbit shank 41, the inertia of head 10 will break shear pin 28 and drivethe inner end of tiring pin 27 into percussive'c'ontact with cap 24. Thelatter will then be tired, exploding element 11 and creating a sharpexplosive shock in the interior of the drill pipe portion through whichelement 11 extends. This sudden explosion will produce a sharp jarringor shaking action of the 'bit and adjacent portion of the drill pipewhich will eiectively loosen or dislodge detritus 43 sufficiently tofree the bit and allow it to be withdrawn from the well.

By reason of its construction and mode of operation, it will be evidentthat the jarring device in accordance with this invention can be runwith a minimum of delay after sticking has occurred so that it can beused effectively to free the bit before there is any substantialopportunity for the detritus to accumulate in large quantity or tobecome strongly consolidated.

The amount of explosive necessary to produce the desired degree ofjarring action will be insufficient to damage the drill pipe, so thatthe device may be safely used in the manner described. The length ofexplosive element 11 may be made as long or as short as desired toimpart the jarring action'to any desired length of the drill pipe. If ajarring shock of increased intensity is desired, element 11 may beformed in a plurality of strands by formingl the desired number of loopsin element 11 and tying the loops together in the manner illustrated inFig. 4.V j

Fig. 3 illustrates a modified form of tiring arrangement by whichVelement 11 maybe tired by hydrostatic pressure in the drilling string.This modification may be employed in instances where it is desired tojar the pipe at some point above its lower end where no abutment ispresentby which the design shown in Fig. 2 could be eiectively set oi.

In the modication shown in Fig. 3, chamber 19 forms a piston chamber inwhich is mounted a slidable piston 5t), carrying on its upper end afiring pin 51 registering with blasting' cap 24. Piston 50 is connectedby means of a link 52 to a screw plug 53 which forms a closure for theouter end of chamber 19. A port 54 is provided in the -wall of chamber19 below piston 50 whereby fluid outside head member 10 may enterchamber 19. Link 52` is designed to rupture when the pressure applied tothe lowerV face of piston 50 reaches some predetermined value. With thisarrangement, the jarring device may be dropped into' tlie drillpip'e andwhen it has sunk into the fluid to adepth at which the hydrostaticpressure, exerted on the lower face of piston 50 by the fluid enteringchamber 19 through port 54, attains the rupture point of link 52, thelatter Vwill break and the pressure of the iluid on the' piston willdrive the latter upwardly, thereby driving firing pin sharply against cap 24, and settingof the explosive element. By appropriate selection ofthe rupture strength of link 52, the device can be made to rire at anydesired position along the interior of the drill pipe where it isdesired to produce the jarring action.

Various other firing mechanisms may be used to set olf the explosivebody. For example, cap 24 may be of the well known electrically red typeconnected to a battery and timing mechanism installed in chamber 19.Such time controlled electrical firing mechanism for setting orfexplosivecharges are well known in the well shooting art.

It will be evident that devices constructed in accordance with thisinvention may' be employed in other applications where it is desired'`to produce an explosion in selected portions of a well bore iilled withliquid. It

may be employed in an open bore hole or inside a pipe string inserted inthe bore hole.

It will be understood that various alterations and changes may be madein the details of the illustrative embodiments herein described withinthe scope of the appended claims but without departing from the spiritof this invention.

What I claim and desire to secure by Letters Patent is:

1. An explosive jarring device insertible in a well pipe or a well bore,comprising, an explosive body of the ilexible cord type, a buoyantmember connected to the upper end of said explosive body, a weightingmember connected to the lower end of said explosive body, said weightingmember having a chamber enclosed therein, a passageway through the upperend of said weighting member communicating with said chamber, said lowerend of said explosive body extending into said passageway, an explosivepercussion cap disposed in said passageway in detonating relation tosaid lower end of said explosive body, and a ring pin movably mounted insaid chamber and adapted to be driven against said cap.

2. An explosive jarring device insertible in a well pipe or a well bore,comprising an explosive body of the flexible cord type, a buoyant memberconnected to the upper end of said body, aweighting member connected tothe' lower end of said body, said weighting member having a chamberenclosed therein, a pasageway through the upper end of said weightingmember communicating with said chamber, said lower end of said explosivebody extending into said passageway, an explosive percussion capdisposed in said passageway in detonating relation to said lower end ofsaid explosive body, a firing pin movably extending through the lowerend of said weighting member to the exterior thereof, frangible meansnormally maintaining said ring means in retracted relation to said capand breakable by impact of said weighting member against an abutment insaid well pipe or bore to drive said firing pin against said cap.

3. An explosive jarring device insertible in a well pipe or well bore,comprising, an explosive body of the exible cord type, a buoyant memberconnected to the upper end of said body, a weighting member connected tothe lower end of said body, said weighting member having a chamberenclosed therein, a passageway through the upper end of said weightingmember communicating with said cham: ber, said lower end of saidexplosive body extending into said passageway, an explosive percussioncap disposed in said pasageway in detonating relation to said lower endof said explosive body, a piston slidable in said chamber, a firing pinmounted on said piston in registration with said cap, a link memberconnecting said piston to the lower end of said chamber to normally holdsaid piston in retracted position relative to said cap, said link beingrupturable by pre-determined iluid pressure applied to the lower end ofsaid piston, and a port in the wall of said chamber below said piston.

References Cited in the le of this patent UNITED STATES PATENTS

